The present invention relates to compressed video systems, and more particularly to video clock and framing signal extraction from a compressed video transport stream by "snooping".
Video and related signals now may be interrelated through their inclusion as members of a functional group. An example is the "Transport Stream" syntax described in ISO/IEC 13818-1, commonly known as the MPEG-2 Stream specification. While this standard describes a means of separating these component or elementary signals and extracting a timebase that may be common to them, video and audio facilities may have a requirement that has greater scope--the synchronization of most or all signals within the facility with a selected incoming or outgoing Program Stream.
In a large facility the place where a given Transport Stream is likely to be decoded is uncertain, and may change according to the tasks being performed within that facility. Furthermore the cost of fully decoding such a stream is considerable.
The content of video production facilities is expected to pass through a network interface device (NID) connecting that facility to a more general telecommunication network. Such a network is likely to use some form of asynchronous, packet-based protocol such as Asynchronous Transfer Mode (ATM). This uncovers an additional need--that of determining for network management purposes the errors in the arrival times of incoming ATM packets.
What is required is an economical means of providing a unified timing means at a content facility and of providing data that may be used for intelligent network management.